Apparatus for cleaning filter screens



Nov. 10, 1953 A. H. BAHNSON, JR 2,658,621 APPARATUS FOR CLEANING FILTER SCREENS Filed June 13, 1950 2 Sheets-Sheet l v INVENTOR BY J NQD/PAN ATTORNEYS 1953 A. H. BAHNSON, JR 2,658,621 APPARATUS FOR CLEANING FILTER SCREENS Filed June 13, 1950 2 Sheets-Sheet 2 Clack Mofa 1N VENTOR BY 1 JWM QJM ATTORNEYS Patented Nov. 10, 1953 UNITED STATES ATENT OFFICE APPARATUS FOR CLEANING FILTER SCREENS 6 Claims.

This invention relates to apparatus for cleaning filter screens and more particularly the filter screen in the washer tanks of an air washer of the central station type. In the latter, water for washing is fed by a pump to spray nozzles located in the air washing chamber. Any foreign matter present in the air such as dust, dirt, lint, etc. incoming to the washing chamber is Washed out by the water issuing from the spray nozzles. The wash water laden with the foreign matter removed from the air is then drained off, filtered through a screen to remove the foreign matter, and then recirculated by the pump to the nozzles.

The foreign matter clings to the filter screen and must be periodically removed to prevent the possibility of clogging the screen which would interfere with free flow of the wash water in the system.

The principal object of this invention is to provide an improved arrangement for cleaning the screen mechanically. Another object is to provide automatic cleaning of the filter screen without interfering with normal operation of the air washer system. Yet another object is to provide an automatic device for cleaning the filter screen cyclically in sections, one section being cleaned while the other is operating and vice versa.

A more specific object is to provide a dam systern for isolating a section of the filter tank on opposite sides of the filter screen coupled with means for draining a the isolated section and initiating operation of screen cleaning spray nozzles after the dams have been erected.

The foregoing as well as other objects and advantages inherent in the invention will be-- come more apparent from the following detailed description of a preferred construction of screen cleaner embodying the invention in conjunction with the accompanying drawings in which:

Fig. 1 is a view in longitudinal vertical section or" a wash water tank filter screen and cleaning device;

Fig. 2 is a view similar to Fig. 1 but showing the various components in the positions taken during the time a section of the filter screen is being cleaned.

Fig. 3 is a top plan view of the multi-sectional wash water tank and filter screen and cleaning device for each section of the tank and screen;

Fig. 4 is a detail; and

Fig. 5 is a diagrammatic View illustrating the timer system by which each section of the filter screen and tank is cleaned periodically in succession.

Referring now to the drawings, reference character T designates a tank having a dirty water inlet 2, at one end thereof, a clean water outlet 3 at the opposite end and a filter screen S extending transversely between the tank side walls 5, 6, intermediate its end walls I, 8. A partition 4 extending longitudinally of the tank intermediate the side walls 5, *3 from end wall i on the upstream side of filter screen 5 divides the tank T interior into two sections Ti and T2.

Each section of the tank is provided with erectable dams on opposite sides or" the appertaining section of the filter screen to the end that the portion of the tank interior intermediate the dams may be isolated from the remainder. Each dam includes a lower fixed section and an upper hinged section. Thus tank section TI containing filter screen section S! is provided with dams 9 and IE3, each having a lower fixed wall section 520., lilo and upper hinged wall section 51), lEb. The water level in the tank is so controlled that when the hinged sections of the dams occupy horizontal positions as shown in Fig. 1, water will flow freely from the inlet end of the tank to the opposite outlet end, the normal level being generally indicated by water line i I. When the hinged darn sections 8b, 56b are raised to vertical position, as shown in Fig. 2, dam ii on the upstream side of filter screen Si will however be effective to prevent further flow of water through tank section Ti.

The other tank section T2 containing section S2 of the filter screen is similarly provided with dams 12, It each having a lower fixed wall section i2a, Na and an upper hinged wall section l2b, 13b.

It will be observed from the drawings, particularly Fig. 3, that the lower stationary dam walls 911, ltd, Na and lSa extend transversely for the entire width of the tank sections Tl, T2. The ends of the upper dam walls, tb, ldb, [2b and 1319, each pivotally connected to the top edge of the associated lower dam wall by a plurality of spaced hinges it, terminate short of the side walls of the tank. Flexible flaps it fastened at opposite sides thereof to the ends of the movable hinged wall sections Sb, lilb, I219, lib of the dams and to the side walls 5, 6 and 4 of tank sections Tl, T2 close the gaps between the ends of the movable dam walls and the tank sides when the upper wall sections of the dams are erected.

Tank section Tl includes a drain plug it in the bottom wall ii for the mouth of drain pipe 31 located between the upstream side of filter screen section Si and dam 9, and tank section T2 includes a similar drain plug l8 for the mouth of drain pipe 22 located between filter screen section S2 and dam [2.

Tank section Tl also includes a horizontally disposed nozzle header pipe 19 situated between the downstream side of the filter screen section SI and dam l0, and tank section T2 likewise includes a similarly arranged nozzle header pipe 20 between filter section, S2 anddam [3. The header pipes I9, 20 are provided with a plurality of spray nozzles 2 I, 23, respectively which direct sprays of water through the filter screen sections SI, S2 in a direction generally; counter to that. in which wash water flows through the screens.

According to the invention, I prefer to couple together the various components of the cleaning device for the filter screens in such; manner that.

as each section SI, S2 of the filter screen is isolated by erection of the dam walls on opposite sides thereof, the drain plug associated therewith will be pulled to. drain off the water trapped between the associated upstream and downstream dams, the associated spray header pipe and nozzle will be given an oscillatory motion and the valve controlling flow of water through the header pipe and nozzles turned on, thus directing sprays of water through the filter screen and cleaning off the upstream side of the screen particularly through the reverse flushing principle.

In order that the various components of each cleaning unit shall operate in the proper sequence, I employ for each unit a fluid motor, the piston of which operates a rock shaft having a plurality of crank arms that are connected respectively by linkage tow the upper hinged wall sections of the upstream and downstream dams and the drain plug. Also used is a float actuated switch controlling operation of the valve supply-- ing water to the flushing nozzles.

The control components associated with section T! of the tank include a fluid motor 25 carried on a bracket 26. secured to tank wall and a horizontal rock shaft 21. mounted in bearings 24; carried by vertical supports 28, 29 upstanding at. the side wall 5' and partition 4. The pivoted upper wall section 95 of dam 9 is connected via spaced links 39 to spaced crank arms 3| on rock shaft 21. Drain plug H5 is connected to another crank arm 32 on shaft. 27' via a flexible chain 33 and guide rod 34 operating in a guide sleeve 35. Plug I6 is secured to the lower end of rod 34, cord 33 is secured to the top of the rod, and a helical spring 36 is used to bias the plug It to closed position over the entrance to drain pipe 31'.

Spaced links 38 connect the pivoted dam wall section lDb to other spaced crank arms 39 on rock shaft 21. The piston 25a of motor 25 isconnected via a link 40 to crank-arm 4| on rock shaft 21. As shown in Fig. 5, motor piston 25a is loaded by spring 2512 to the left, i. e. in such direction as will cause clockwise rotation of rock shaft 21, as viewed in the drawings, and movement of the upper dam walls 91), lilb to horizontal position in tank section Tl. Also with the motor piston 25a in the extreme left position as shown in Fig. 1, there will be ample slack in the pull cord 33 to enable lowering of the drain plug IE to its closed position.

When motive fluid such as air or liquid under pressure is introduced to the cylinder 250 of motor 25 through valve 43, piston 25a is forced to the right thus turning rock shaft 21 to the position shown in Fig. 2, thus erecting the dam walls 9b, Nb, and pulling cord 33 and hence drain plug it upwardly off its seat. As previously explained,

'4 erection of the dam walls and removal of the plug isolates that portion of tank section Tl between darn walls 9 and I5 and permits the water in the isolated section to drain off through pipe 31.

The horizontally arranged spray header pipe i9 associated with tank section TI is mounted at its ends in bearings 44 on the tank side walls 5 and 4 for oscillation on its support axis. A crank arm 45 secured to pipe 19 is connected by link 46 to the piston 41a of another fluid motor 47 supported on bracket 48 secured to the partition wall 4. Piston 41a is loaded by spring 411) upwardly towards that. end of the cylinder 410 into which the motive fluid is introduced periodically thus effecting periodic reciprocation of piston 41a and like periodic oscillation of header pipe I9.

As will be explained later in further detail, oscillation of header pipe 19 starts automatically as the water trapped between dams 9 and I0 drains off, the desired control being effected electrically by means of a switch controlled by a pivotally mounted float arm 49 located in tank section TI on the downstream side of filter section Si.

The dams and drain plug associated with tank section T2 are controlled by mechanism identical with that which has been described in. detail above for tank section TI, and in the interest; of simplifying the description, I have considered it sufficient merely to identify the control components of tank section T2v corresponding to like components of tank section TI, by the same reference numerals but with primes added to the former to distinguish them from the latter. The

-.. rock shaft in tank section T2 and its supports have likewise been assigned the same reference numerals that designate. corresponding components in the tank section Tl, but with primes. added thereto.

With reference to Fig. 4 in particular, it will be observed that only one motor 41 is used to oscillate the header pipe 20 in tank section T2 as well as header pipe i9 in tank section Tl. A separate motor could of course be used for each header pipe but since water is admitted only to the particular header pipe of the screen section S'l or S2 being cleaned, there is no objection to oscillating both headers together by a common motor.

As explained in the introductory portion of this specification, I prefer to clean first one section of the filter screen S and then the other to the end that the air washing system can continue in operation while the screen is being cleaned. I also prefer to have the cleaning of the screens done automatically in a timed cycle. With these two objectives in mind, reference should now be made to Fig. 5 which illustrates a suitable control system that operates over a cycle that repeats itself indefinitely so long as it remains in operation.

A timer motor 53 which can be of the clockwork type is used to rotate a shaft 54 and an electrically conductive contact arm 55 attached thereto counterclockwise at a uniform angular velocity: dependent upon the particular length of cleaning cycle desired. Arm 55 carries two contacts 56, 51 which are so located radially of the center 0 of arm rotation that they will wipe over two corresponding sets ofarcuate contact strips 58, 53 and 60, 51- disposed diametrically of each other on a support plate 52 of insulating material. Contact strips 59 and 60 are shorter than strips 58, (ii and so placed that contact 51 engages strips 58 and SI- a considerable time in ad- Vance of engagement between contact 56 and its associated contact strips 59, 60. However, contacts 56, 51 break away from the two sets of strips 58, 59 and 60, 61 at the same instant. The reason for this arrangement will be explained hereinafter.

An electric motor 53 which also runs at a uniform speed has mounted upon its shaft 64 an electrically conductive contact arm 95 adapted to wipe over four equally spaced arcuate contact strips 65 mounted on a support plate 61 of insulating material.

The two-way valves 43, 43 associated with fluid motors 25, 25' are controlled by solenoids 59, 58' whose armatures 68a, 68a are loaded by springs 68?), 68b in such direction as to cut ofi the supply of compressed air entering at pipes 69, 69' from the motor cylinders 25c, 25c and place the latter in communication with pipes "Ill, 79' leading to atmosphere when the solenoids are in a deenergized condition. The solenoids are shown in this position in Fig. 5.

Motor 41 which oscillates the spray header pipes i9, 20 is also controlled by a similarly constructed two-way valve H having a compressed air inlet pipe 12, and a pipe 13 for placing the motor cylinder 41c in communication with the atmosphere. Valve H is actuated by a solenoid it whose armature 14a is loaded by spring 141) in such direction as to cut oil the air supply pipe 12 and place the motor cylinder in communication with the atmosphere when solenoid 14 is in a deenergized state.

Water under pressure is supplied to the outer end of spray header pipe I9 through valve 15 controlled by solenoid 76 whose armature 16a is loaded by spring 1612 in such direction as to cut off the supply of water from inlet pipe 1! to header pipe l9 when the solenoid is in a deenergized state. Water is supplied to the outer end of spray header pipe 20 by similarly arranged components which for sake of simplification have been assigned corresponding reference numerals but with primes added thereto.

The remaining components of the automatic control consist of a switch 18 the contacts of which close as the float 49 lowers and open when it rises, and a similar switch 18 associated with float 49.

The control operates in the following manner:

Assuming contact arm 55 to be in the position shown but rotating slowly in the direction indicated by the arrow, all components will occupy the positions shown in Fig. 5. As contact 51 reaches the upper end of contact strip 58, a circuit for energizing solenoid 68 from a source of power supply '19 will be completed via conductors so, 8 i, arm 55, engaged contacts 51, 58, conductor 82, the winding of solenoid 58, and conductors 83, 8d. Energization of solenoid 6B actuates valve 43 from the position shown to its other position placing compressed air inlet pipe 69 in communication with motor cylinder c and causing piston 25a to move to the right and rock shaft 21 from the position shown in Fig. 1 to the position shown in Fig. 2. Such movement of shaft 27 erects the movable dam walls 9b, Iflb, in section Tl of the tank, and pulls out drain plug [6. Erection of dam walls 91;, 10b stops the how of wash water through tank section TI, and the water trapped between the dams 9, it flows out the drain pipe 37.

Float 49 follows the level of the water being drained through pipe 31 and ultimately drops far enough to close switch contacts I8 which completes a circuit for energizing and starting motor 6 63 from the power source 19. This circuit may be traced from one side of source 19 through conductors 80, 85, motor 63, conductor 86, switch contacts 18 and conductors 81, 84 to the other side of power source 19.

All four of the contact strips 66 are connected together and via conductors 83, 86, switch contacts l8 and conductors 81, 84 to one side of power source 19. Contact arm 65 is connected via conductor 89 to one side of the winding of solenoid 14, and the other side of the winding of solenoid I4 is returned to the other side of power source 19 through conductors 99, and 80. Thus each time arm engages one of the contact strips 66, solenoid 14 will become energized thus opening valve H to admit compressed air to motor cylinder 41c and driving the piston 41a downward to rock the spray headers I9, 20. When contact arm 65 is between adjacent contact strips 66, the energizing circuit of solenoid 14 is open. Thus as contact arm 65 breaks contact with each strip 66, solenoid 14 deenergizes thus moving valve 'II to its other position where motor cylinder 410 is placed in communication with the atmosphere. This allows loading spray 41b to return piston 41a to its starting position and rock the spring header shafts in the opposite direction. Motion of the motor piston 41 is thus periodic thus imparting an oscillatory motion to the spray header pipes I9, 20.

By the time that contact arm 55 has rotated far enough to engage the other and shorter contact strip 59, the water trapped between dams 9 and I!) will have had an opportunity to drain out. Engagement between contact 56 and contact strip 59 completes a circuit for energizing solenoid 1B, the circuit being traced from one side of power source 19 through conductors 80, BI, arm 55, engaged contacts 56, 59, conductor 9|, the winding of solenoid 16, and conductors 92, 84 to the other side of source 19. Energization of solenoid 76 actuates valve 15 to open position, and water for reverse flushing of the filter screen section S! to clear away the dirt lodged in the filter screen and particularly against the surface of the screen on the upstream side is then admitted to spray header [9, discharging through spray nozzles 21.

The amplitude of oscillation of the spray nozzles 2| is sufliciently great to enable the sprays discharged from the nozzle to sweep the filter screen section Si from top to bottom, and the nozzles 21 are spaced sufiiciently close together along the entire length of the spray header pipe l9 as to assure complete cleaning of the screen section SI throughout its entire width. This arrangement provides clearing of the entire area of the filter screen, and the dirt, lint, etc. removed from the screen is washed down the drain ipe 31.

Reverse flushing of the filter screen section SI continues until contacts 56, 5! break simultaneously with their associated contact strips 58. 59. When this occurs, solenoid 75 becomes deenergized thus closing valve 15 and shutting oiT flow of water to spray header pipe l9. Simultaneously, solenoid 58 becomes deenergized, moving valve 43 to its other position allowing piston 25:! to move back to its starting position under the restoring force of spring 2517, and rocking shaft 2? to the position shown in Fig. 1 thus lowering dam walls 91), I91) and dropping drain plug l5 into closed. position over the entrance to drain pipe 3?.

The tank section Tl thus again fills with washing water, and the circulating pump (not shown) will. draw water through the: outlet :3

from both: sections ITI, 372 of the tank. iWhen the 1 tank section between-dams Stand. lt'rrefills,

'fioat t9 will rise to openthecontacts of switch I8 thus deenergizing and stopping .imotor 163 which in turn stops oscillationof motorzpiston and :the drain plug :ls pulled upward. -Water trapped between dams l2and t3 willithemdrain out causing closureof fioat switch-contacts 13' which is efiective to start contact motor'ifiazagain and set spray header pipes :19, 20.into-;oscillation. When contact 56:on*arm 55.reaches contactstrip 8t, solenoidlfi becomes energized :to open valvelfi' and admit water underzpressure to spray header pipe 2!! for. reverseflushing'and cleaning of; filter section S2.

Reverse flush-ing of filter section S2 continues until contacts 56, 51 leave contact .StIiDSn'Bfly. simultaneously, at whichinstant-valve 1'15 is :cut off to stop flow of water through nozzles223,1:and

shalft 21 rocked back to its other poSitionfOlding down damwalls 2b, l3b, and :reinserting drain 'pl-ug'IB in the'mouth of'drain pipe 22. Tank section'Tz willthen refillzopening switch contacts 18 to: stop-motors GSJand H and washing water for the air will again be passedthrough filter sectionSZto'the tank outlet-.3. "This completes a complete cleaning cycle.

Both sections SI, S2 of the filter willithenremain in operation until contact 51 Jon contact arm 55 again reaches contact .striprEBthereby to'begin the cleaning cycle anew.

As shown in Fig. l, the centralxpartitionefl. has a portion to cut away at the end-wall B'cfithe tank and a similar cut-away'portionat'the.end wall'l. Thepurpose of thesezisito'allowifree flow'ofwater'into both sections TI, .T2zof the tank from the single inlet pipe Twhich .enters section T2 through wall 6, and free'outfiow from both tank sections into the single'outlet pipe 3 which also enters section T2 through wall 6. Thus while section SI of the filter screen is being cleaned, dirty wash water from -the 'air washing chamber is still-free to pass from inlet 2 through tank section T2 an'dfilter screen-S2 and thence out through pipe 3into a pump fOr recirculation in the air washing chamber. Likewise, when section S2 of the filter screen is being cleaned, tank section Tl remains in operation filtering the dirty wash water through qfilter screen Si. In this manner, the'system never has to be'shut down 'forcleaning oft-he filters thus permitting continuous operation of the air washer.

In conclusion, I-wish it to be expressely understood that while the foregoing illustrated embodiment of my improvedfilter screencleaning apparatus is preferred, various detail changes in the construction and arrangement of the component parts may be madewithout however departing from the spirit and scope of my invention as defined in the appended claims.

I claim:

'1. Filter apparatus comprising a tank having a partition member extending longitudinally thereof :intermediate the =.tank side walls and .dividing:theainterior.of the tankinto a pair-of Ltankflsectionscthrough which'liquid is adapted vtoriiow; a filtersplaced crosswise of the direction of liquid flow in each tank section; a liquid inlet toxbothsections onthe upstream side of thefilterspra liquid outlet ;from both sections on the downstream side .of said-.filters; each said tank section including varpair of dams erectable'respectively on the upstream and downstream sides of said filter to isolate thatportion of the tank interior between the said twodams from .theiremainder'of the tank interior, :a normally closed-drain disposed between said filter'and the dam upstream therefrom, :a valve controlled flushing device disposed between said filter and the dam located downstream therefrom for directinga flushing fluidthrcugh the filter in a gen- :erally upstreamdirectiommeans for erectingsaid fdamsrandropening said drain and for lowering said dams and re-closing'sai'd draimand means openingthe valve on said 'fiushing device'rwhen said dams'areI-erected; and control means '01)- crating the dams 50f each-tank section in sequence such that the damsofonly one section are erected at anyone time. thereby cleaning. the filterzofone tank section while the other remains in operation.

2.?Filten apparatus comprising a. tank; a .partitiondividing the'interiorofsaid tank into a pair:of tank sections througheach of which a stream of liquid to be filtered is adapted'to flow; each said tank sectionincludinga filter'placed crosswise 'of -thedirection of liquid flow through the section, a paino'f dams placedcrosswise of the section 'located respectively upstream and downstream 'fromthe filter, eachsaid dam including a "lower vertical stationary portion and an upper portion hinged to said lower portion for movement about a transverse axis-into-a position substantially coplanar'with saidlower portion, thereby to blockoff further flowof liquid through the section, a drain'from the tank interior disposed-between said filter and the dam upstreamtherefrom, a-closuremember for the mouth of said drain, a plurality'of spray nozzles carried by -'a header pipe-oscillatory about its axis and disposed between said filter and the dam downstream therefrom adapted 'to direct flushing-fluid through the filter in a generally upstream direction, a "rock shaft extending crosswise of the tank section, linkage means connecting-the'movable': portions of both dams with crank arms on said rock shaft, means connecting the closuremember for said drain with'another crank arm on said rock shaft,-the crank arms on said rock shaft being arranged so that said closure member is lifted from the mouth of said drain-when the upper'portions of said dams aremoved= to theirpositions blocking ofi liquid flow through the section, and a motor controlling rotation of said rockshaft; a secondmotor for setting the spray header pipes of both tank sections'into'oscillationyand a'timer device for actuatingthe motors controlling the 'dams of the for liquid flow therethrough between aid inlet and outlet, a filter placed crosswise of said channel for filtering the liquid flowing therethrough, a pair of damming devices located respectively upstream and downstream from said filter, an outlet drain from said channel disposed between said filter and the damming device located upstream therefrom, means for opening said drain and actuating said damming devices from a non-damming position to a damming position transversely of said channel wherein the channel portion therebetween is isolated from the remainder of the liquid in said tank and for re-closing said drain and re-actuating said damming devices to their non-damming position, a valve-controlled flushing device for said filter disposed between said filter and the damming device located downstream therefrom for efiecting reverse flushing of said filter, and means for automatically opening sa d valve on said flushing device when said damming devices are disposed in their damming position and for closing said valve when said damming devices are disposed in their non-damming position.

4. A filter tank as defined in claim 3 wherein each said damming device comprises a lower stationary wall section disposed transversely of said channel and an upper wall section hinged to said lower section for swinging movement into a substantially vertical position and which is connected to the said actuating means for said damming devices.

5. A filter tank as defined in claim 4 wherein the upper hinged wall section of said damming device is spaced from the tank wall forming the sides of said channel, the gap between the ends of said hinged section and tank walls being bridged by a flexible flap.

6. A filter tank as defined in claim 3 wherein said device for reverse flushing of the filter comprises a header pipe having a plurality of nozzles, said header pipe being placed transversely of the channel, and means imparting an oscillatory motion to said header pipe about it longitudinal axis.

AGNEW H. BAHNSON, JR.

Name Date Dunbar Jan. 15, 1918 Hughes Oct. 15, 1940 Number 

